1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, and more particularly to an electrophotographic photosensitive member having a photosensitive layer containing a specific compound. This invention also relates to a process cartridge and an electrophotographic apparatus which have such an electrophotographic photosensitive member.
2. Related Background Art
Electrophotographic photosensitive members making use of organic photoconductive materials have greatly been improved in their sensitivity and durability (or running performance) as a result of the advancement of function-separated photosensitive members comprising a charge generation layer containing a charge-generating material and a charge transport layer containing a charge-transporting material which are superposed, and have been widely put into practical use.
Meanwhile, in recent years, photosensitive members having a broad spectral sensitivity ranging from visible to infrared wavelength regions are energetically developed so that copying machines can be made to have the function of writing by laser light. As a means for achieving such an object, it is known to use a charge generation layer formed of a charge-generating material having a sensitivity in the visible light region and a charge-generating material having a sensitivity in the infrared region which are mixed with each other or superposed in layers.
Printers to which electrophotography is applied are in wide use as terminal unit printers. These are chiefly laser beam printers having lasers as light sources. As the light sources, semiconductor lasers are used in view of the cost, the size of apparatus and so forth. Semiconductor lasers prevalingly used at present have an oscillation wavelength as long as 790 to 820 nm. Accordingly, electrophotographic photosensitive members having sufficient sensitivities in such a long-wavelength region are being developed, and, in order to improve sensitivity and running performance, it is known to use the charge transport layer formed of charge-generating materials which are mixed with each other or superposed in layers.
As a combination of an azo pigment with a phthalocyanine compound, Japanese Patent Application Laid-open No. 7-175241 disclose a photosensitive member making use of a specific azo pigment and an oxytitanium phthalocyanine; and Japanese Patent Application Laid-open No. 7-128888, a photosensitive member making use of a specific azo pigment and a gallium phthalocyanine.
These photosensitive members, however, are disadvantageous in that the properties of the respective charge-generating materials can not well be exhibited and, especially when used in a mixture, their potential variations become great during running as memory characteristics become poor. Use of the gallium phthalocyanine may result in a poor chargeability to cause image deterioration due to dots or fog. Also, it can not be said that the sensitivity itself in the visible and infrared regions are satisfactory.